TV footage showed firefighters dousing the charred remains of a car. A Reuters journalist earlier saw a cloud of smoke in Arbil, but it was not clear whether it was from a blast.

Three near-simultaneous car bombs exploded in the northern Iraqi city of Kirkuk on Saturday, killing 20 people and wounding 65, a senior police officer and a doctor said.

Two of the bombs exploded near buildings under construction that were used as observation positions by security forces, while the third struck the entrance to a market.

The bombings come as Iraqi federal and Kurdish security forces battle a jihadist-led militant offensive that was launched in June and has overrun large areas of five provinces.

In the early days of the onslaught, Iraqi soldiers left their positions in oil-rich Kirkuk province, the capital of which is the city of the same name.

This cleared the way for Kurdish forces to take control of it and other disputed northern areas that they have long wanted to incorporate into their autonomous region, over the strong objection of Baghdad.

An advance by Islamic State and the Levant through northern Iraq has alarmed the Baghdad government and its Western allies and drawn US airstrikes in Iraq for the first time since the withdrawal of American troops in 2011.

Although the air campaign has caused a few setbacks for Isil, they do not address the far broader problem of sectarian warfare which the group has fueled with attacks on Shiites.

Bombings, kidnappings and execution-style shootings occur almost daily, echoing the dark days of 2006-2007, the peak of a sectarian civil war.

Two of Iraq's most influential Sunni politicians suspended participation in talks on forming a new government after the militiamen carried out the mosque attack.

Deputy Prime Minister Saleh Mutlaq and Parliament Speaker Salim al-Jibouri have pulled out of talks with the main Shiite alliance until the results of an investigation into the killings are announced.

Jibouri, a moderate Sunni, condemned both Islamic State as well as the Iranian-trained Shi'ite militias who Sunnis say kidnap and kill members of their sect with impunity.

"We will not allow them to exploit disturbed security in the country to undermine the political process. We believe the political process should move on," he told a news conference on Saturday.

Iraq's new Shiite prime minister, Haider al-Abadi, faces the daunting task of trying to draw Sunnis into politics after they were sidelined by his predecessor Nouri al-Maliki.